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bsd_signal

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

bsd_signal - signal handling with BSD semantics

LIBRARY

Standard C library (libc,~-lc)

SYNOPSIS

#include <signal.h>
typedef typeof(void (int))  *sighandler_t;
sighandler_t bsd_signal(int signum, sighandler_t handler);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)): bsd_signal():

    Since glibc 2.26:
        _XOPEN_SOURCE >= 500
            && ! (_POSIX_C_SOURCE >= 200809L)
    glibc 2.25 and earlier:
        _XOPEN_SOURCE

DESCRIPTION

The bsd_signal() function takes the same arguments, and performs the same task, as signal(2). The difference between the two is that bsd_signal() is guaranteed to provide reliable signal semantics, that is: a) the disposition of the signal is not reset to the default when the handler is invoked; b) delivery of further instances of the signal is blocked while the signal handler is executing; and c) if the handler interrupts a blocking system call, then the system call is automatically restarted. A portable application cannot rely on signal(2) to provide these guarantees.

RETURN VALUE

The bsd_signal() function returns the previous value of the signal handler, or SIG_ERR on error.

ERRORS

As for signal(2).

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
bsd_signal()	Thread safety	M-Safe

VERSIONS

Use of bsd_signal() should be avoided; use sigaction(2) instead. On modern Linux systems, bsd_signal() and signal(2) are equivalent. But on older systems, signal(2) provided unreliable signal semantics; see signal(2) for details. The use of sighandler_t is a GNU extension; this type is defined only if the _GNU_SOURCE feature test macro is defined.

STANDARDS

None.

HISTORY

4.2BSD, POSIX.-2001. Removed in POSIX.-2008, recommending the use of sigaction(2) instead.